This invention relates to a metal melting tool such as a plasma arc torch or a laser for performing cutting operations on an underlying metal workpiece. An exemplary plasma arc torch is disclosed in Sturges et al U.S. Pat. No. 5,079,403 while a typical laser cutting tool is disclosed in Scott et al U.S. Pat. No. 4,550,241.
In tools of the above type, it is important to maintain a constant but adjustable vertical spacing or standoff height between the working tip of the tool and the underlying workpiece. When the tool is, for example, a plasma arc torch, it is necessary to adjust the stand-off height depending on factors such as the rated amperage of the torch and/or the thickness of the particular workpiece.
Prior mechanical systems for adjusting the stand-off height of a metal melting tool require several components, require time-consuming adjustments to be made and, in some cases, require the use of a gage between the tool tip and the workpiece to establish the desired stand-off height. Electronically controlled stand-off height adjusting systems enable much quicker and easier adjustment but such systems are complex, have a high initial cost and are expensive to repair.